This study is to validate the dose of V cholerae MO10 which will consistently induce diarrheal illness in nonimmune volunteers. Symptoms will be monitored following administration, and treatment given for any illness which may result Samples of serum and stool will be collected to document the excretion of virulent V cholerae O139 and the vibricidal antibody IgG and IgA antitoxin antibody titer will be measured.